Abstract:

The BVOC emission fluxes were calculated using an empirical model of BVOC emissions driven by the observed solar radiation and meteorological data measured from May 2013 to December 2016 at a subtropical Pinus plantation in Taihe county, Jiangxi province, China. The interactions between the BVOC emission fluxes and their forcing factors were investigated by dividing the atmospheric substances, S/Q values (S and Q are defined as horizontal diffuse and global solar radiation) into small groups with an interval of 0.05 between 0 and 1. Similarly, the BVOC emission fluxes and other parameters (PAR, air temperature, water vapor pressure, S/Q) were also divided to small groups with the same interval as the S/Q values. The relationship between the averaged BVOC emissions and other variables was investigated in each S/Q interval, and the following conclusions could be made. The emission fluxes of isoprene, monoterpenes and BVOCs (isoprene+monoterpenes) (1) increased with the increase of PAR when PAR was less than 1180 μmol∙m^-2∙s^-1, and monoterpene emissions were more sensitive to the changes of PAR than the isoprene emission, (2) increased with the increase of air temperature, reached its peak when the air temperature raised to 26 ℃, but decreased with the further increase of air temperature, (3) increased with the increase of water vapor pressure, reached its peak when water vapor pressure raised to 24 hPa, and decreased with the further increase of water vapor pressure, (4) increased with the increase of S/Q when S/Q≤0.55, and decreased with the increase of S/Q when S/Q≥0.55. Therefore, PAR, air temperature, water vapor pressure and S/Q are key factors influencing BVOC emission fluxes, and S/Q is a critical factor in controlling the positive and negative interactions and their turning points from the positive to negative interactions between BVOC emissions and their driving factors (PAR, air temperature, water vapor pressure, S/Q). The strategy used in this study by dividing the atmospheric substances (S/Q) into small intervals and investigating their relationships between BVOC emission fluxes and other variables in each S/Q intervals demonstrated the improvement of our understanding to the physical, chemical and biological processes and their interactions, as well as chemical and photochemical mechanisms associated with BVOC emissions. This proposed method could favor the future study, and the empirical model of BVOC emissions discovered a competition mechanism in SOA formation from oxidation of isoprene and monoterpenes.

Key words: biogenic volatile organic compounds (BVOCs), emission flux, photosynthetically active radiation (PAR), empirical model, influencing factor, secondary organic aerosol (SOA), water vapor content, scattering factor

摘要：

利用植物挥发性有机物（BVOCs）排放经验模式以及太阳辐射、气象参数测量数据,计算了2013年5月—2016年12月年江西省亚热带人工林BVOCs的排放通量。为了深入研究BVOCs排放与其控制因子之间的相互作用,将大气中物质含量（以S/Q表示,S、Q分别为水平面散射辐射和总辐射）在0.0—1.0区间以0.05间隔分区,同时将BVOCs排放通量、其他参数一同分区,计算了所有参数在每个分区的平均值。进一步研究了对应于所有S/Q分区的BVOCs排放通量与其影响因子（PAR、气温、水汽含量、S/Q）之间的相互关系。研究发现,异戊二烯、单萜烯、BVOCs排放通量,（1）在PAR<1180 μmol∙m^-2∙s^-1的条件下,均随PAR增加线性增加,单萜烯排放比异戊二烯排放对于PAR的响应更加敏感。（2）随气温的升高而增加,当气温达到26 ℃时达到峰值;然后随气温的升高而下降。（3）随水汽含量的增加而增加,当水汽含量为24 hPa时达到峰值,之后随水汽含量的增加而下降。（4）当S/Q≤0.55之时,随S/Q的增加而增加;当S/Q≥0.55后,随S/Q的增加而下降。PAR、气温、水汽含量、S/Q共同影响着BVOCs的排放,其中大气中的物质含量S/Q是一个关键参数,它控制着BVOCs随其主要影响因子（PAR、气温、水汽含量、S/Q）变化的正负作用及其转折点。将大气中物质含量分区,研究各个分区内BVOCs排放通量和其他各个参数之间的相互关系,有助于深入了解与BVOCs排放有关的物理化学生物过程及其相互作用、化学和光化学机制。建议将这一方法用于未来研究。BVOCs排放模型揭示出异戊二烯和单萜烯在生成二次有机气溶胶方面存在竞争或相互抑制的机制。

关键词: 生物挥发性有机物, 排放通量, 光合有效辐射, 经验模式, 影响因子, 二次有机气溶胶, 水汽含量, 散射因子